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Study of Tadalafil in BMD Revised, Reopened

Update (Nov. 9, 2012): This story has been updated to reflect that recruitment for this study ends Dec. 31, 2012.

An MDA-supported, short-term trial of the vasodilating drug tadalafil (Cialis) in teens and men with Becker muscular dystrophy (BMD) has undergone some minor restructuring and is now open to 12 additional participants.

Lack of availability of the MRI (magnetic resonance imaging) device during specific periods of time was the reason for redesigning the trial, according to principal investigator Ronald Victor.

Victor, a cardiovascular disease specialist at Cedars-Sinai Medical Center in Los Angeles, has an approximately $1 million grant from MDA to conduct this trial.

The study, which originally opened in early 2010 and temporarily closed to new participants in June 2012, is being conducted to see whether tadalafil can enhance blood flow to exercising muscles.

Tadalafil may counteract some effects of lack of dystrophin

Tadalafil, marketed by Eli Lilly as Cialis, belongs to a class of drugs known as phosphodiesterase inhibitors. Sildenafil (Viagra) also belongs to this group.

Inhibiting phosphodiesterase type 5 (PDE5), the specific action of tadalafil, relaxes the smooth muscles that line blood vessels by enhancing the release of nitric oxide from nerve terminals and blood vessel cells. This action, which enhances penile erection, also may improve blood flow to skeletal muscles and the heart.

BMD and the related Duchenne muscular dystrophy (DMD) result from a partial (in BMD) or complete (in DMD) deficiency of the dystrophin protein at the muscle-fiber membrane; a downstream effect of dystrophin deficiency is a lack of exercise-related vasodilation.

Experiments in mice with a deficiency of the dystrophin protein in their muscles have suggested that the drug may increase blood flow to exercising muscles and thus alleviate the exercise-related fatigue experienced by people with BMD.

Restructured study will require two short visits to LA

During the screening part of the study, participants with and without BMD will undergo blood chemistry tests; a leg muscle biopsy; ultrasound studies of blood flow before and after handgrip exercise; and MRI scans of the forearm muscles before handgrip exercise and 24 and 48 hours after handgrip exercise.

This screening phase of the study will determine which BMD-affected participants meet study criteria for the second (medication) part of the trial.

During the medication phase — one to two weeks later — 12 men with BMD will repeat the handgrip and imaging testing after receiving two doses of tadalafil or two doses of a placebo on two consecutive days.

There is a three in four chance that each participant will receive tadalafil, and a one in four chance that he will receive a placebo.

To participate

The study is currently recruiting 12 additional participants who:

have proven BMD;

are ages 15 to 55;

are ambulatory (can walk);

have a normal echocardiogram (heart imaging test);

are able to perform the handgrip exercise protocol; and

can come to Los Angeles twice in one month.

There is no cost to participate, and parking will be validated. Recruitment ends Dec. 31, 2012.

For more background information, see Tadalafil in Becker Muscular Dystrophy; or enter NCT01070511 in the search box at ClinicalTrials.gov. (Note: As of Sept. 28, 2012, the ClinicalTrials.gov listing does not reflect the need for 12 additional participants or the redesign of some aspects of the study.)

About Clinical Trials

A clinical trial is a test, in humans, of an experimental treatment. Although it's possible that benefit may be derived from participating in a clinical trial, it's also possible that no benefit, or even harm, may occur.

MDA has no ability to influence who is chosen to participate in a clinical trial.